“I was online trying to locate an article when I stumbled on the piece titled “Keeping Router Collar Guides Tight.” I am not trying to say that there is anything wrong about the suggestion to use plumber’s Teflon® tape to keep guide bushing nuts from vibrating loose, but I believe that there is a better way to solve this safety issue.
“You can find for sale guide bushing spring lock washers, more commonly known as wave washers, for this exact purpose. I am actually surprised that these are not more widely available or used by more woodworkers, because a guide bushing coming loose during an extended use of that setup is actually quite dangerous. I have ordered several sets and have them in several dedicated router setups and as part of other router bit sets. Being a professional woodworker, I have had a guide bushing nut come loose one time and thought that was a very dangerous situation where someone (me) could have gotten hurt. Then, when you consider the fact that some manufacturers still use steel guide bushings in their kits, you just have to go ‘Wow.’ In my shop, these are always used with every guide bushing setup by me and by students when I teach a class.” – Mark Klosky